There is described in EP-B1-0 024 802 a gas turbine blade fabricated from a nickel-based alloy which is provided by the plasma arc spraying technique with an overlay coating of CoCrAlY. This coating may suffer from microporosity and is therefore given a further coating of aluminium by a pressure pulse chemical vapour deposition process. This two stage process has been found to give good results but is expensive and it is thought that it is not in commerical use. Two processes for the production of overlay coatings which are used for the purpose described are plasma spraying and electron beam techniques. However, these are both expensive.
It is accordingly an object of the present invention to provide a coating which has good properties while being reasonable in price.